Over relatively recent times, satellites have proven to be indispensable for universal communication networking in support of a variety of personal, commercial, and security applications. With key innovations including spatial reuse of spectrum with spot beams, affordable user terminals, and use of higher radio bands such as Ka-band, commercial satellite networks currently provide broadband services to enterprises, governments, educational institutions and even consumers. Digital packet processing, almost universally used in contemporary voice, data, video and business networks, facilitates flexibility, affordability, and efficiency in transporting information using common protocols. Communications satellites themselves, however, generally have stayed with traditional transponded designs involving analog signal frequency-band conversions, filtering and signal amplification, without inclusion of regenerative packet processing and routing capabilities. Digital signal and upper layer packet processing that has revolutionized ground networking components, including those belonging to communications satellite systems, has generally not influenced the communication satellite payload designs. Aside from a few notable exceptions with onboard packet processing capabilities (such as the experimental IP Router in Space (IRIS)—see, e.g., Cuevas, E., et al., “Preliminary results of a technology demonstration of the internet routing in space capability over a geostationary communications satellite,” IEEE MILCOM 2010; and the current commercially deployed Hughes SPACEWAY® satellites—see, e.g., Whitefield, D. Arnold S., Gopal, R., “SPACEWAY now and in the future: on-board IP packet switching satellite communication network,” IEEE MILCOM 2006), the satellite size, weight and power (SWaP) constraints, system complexity and costs, and space qualification costs have typically limited the use of powerful digital processing capabilities in satellite payloads.
The most prevalent example of packet networking is the IP-based scheme of the global Internet, which facilitates the transmission of packetized data between end hosts via multiple network IP router node hops over a vast geographical areas around the globe. The use of IP packets over the Internet via a variety of transport media such as satellite, copper, terrestrial, wireless and fiber enables high bandwidth connectivity amongst billions of hosts. Dynamic protocols allow the end hosts and applications to identify remote peers and packet data is routed over a path comprising multiple IP routing nodes. Dynamic standards-based routing protocols allow the use of appropriate shortest paths comprising these IP routers. Basic packet routing is augmented with additional Quality of Service (QoS) and traffic engineering considerations to manage packet transport characteristics comprising data rate, delay, packet loss, and jitter. Although addressing and routing protocols (such as Domain Name System (DNS), Dynamic Host Configuration Protocol (DHCP), Open Shortest Path First (OSPF), Border Gateway Protocol (BGP)) are widely deployed to support best-effort transport, additional features for better defined and more predictable packet transport are selectively offered only as premium service (using protocols such as Multiprotocol Label Switching (MPLS), Multiprotocol-Border Gateway Protocol (MP-BGP), Resource Reservation Protocol—Traffic Engineering (RSVP-TE), Third Generation Partnership Program—Long Term Evolution (3GPP LTE) and Differentiated Services Code Point (DSCP)).
With overprovisioning, even a best-effort approach provides adequate wired network transport performance for most applications within enterprises and even over the public Internet. For high priority applications or when link and node resources are constrained, a more disciplined and expanded use of advanced traffic engineering and packet processing protocols is warranted which results in additional functions to be hosted by the network nodes. Besides higher layer packet processing, satellite networks also require suitable radio links, involving coding, modulation, and Media Access Control (MAC) functions to operate with shared radio resources (frequency spectrum and power). For high capacity nodes, physical layer functions such as coding and modulation require hardware implementation, using performance field programmable gate arrays (FPGAs) or application specific integrated circuits (ASICs). Higher layer packet processing functions such as header and payload compression, encryption, segmentation and assembly, and packet processing (such as classification, policing, queuing, scheduling) in the user data plane also warrant hardware implementation.
Further, the upper layer control plane functions, such as MAC, channel management, mobility management, and Layer 3 (L3) control functions, for addressing, routing, QoS, and traffic engineering require significant software solutions. Software is needed to support complex two or multi-party protocol implementations and to continue to accommodate changes for correcting design errors and addressing security vulnerabilities, and to add new features associated with design enhancements and protocol evolution. Such software solutions are generally addressed via standardize protocols, administered by standards setting organizations such as the European Telecommunications Standards Institute (ETSI) and the Telecommunications Industry Association (TIA). The standards working group for such upper layer software solutions are typically dominated by terrestrial network service and equipment providers, and thus do not necessarily address satellite-specific constraints and performance objectives (such as larger satellite propagation delay, movement of near-Earth orbit satellites relative to fixed user terminals, longer satellite lifetime, etc.), which can make satellite-based implementation even more problematic.
Satellite and aerial networks are hosted by platforms with limited size, weight and power (SWaP) constraints, and require efficiencies in radio and digital processing resource use at physical, link and network layers. User data packetization helps improve efficiency, but also imposes further requirements for digital processing in the respective networking nodes. Further, in addition to the SWaP constraints that satellite and other aerial platforms are subject to, unlike terrestrial networks where nodes can be routinely upgraded with new hardware, satellites are also subject to high deployment costs and are generally not upgradeable once deployed—thus each and every function and requirement must be carefully analyzed and designed with as much expansion and upgrade potential for the initial satellite design, and the associated hardware and software must be extensively tested throughout the design and production process and during an extensive post-production and pre-launch period. In recent years, however, with the rapid development of satellite technology, including on-board processing or on-board packet switching and inter-satellite communications links, satellite and other airborne network devices (such as satellite or space Internet Protocol (IP) routers and airborne high altitude platform (HAP) routers) have become viable options for commercial networks. Further, the successful launch and commercial operation of the Hughes SPACEWAY® satellites, employing Ka-band spot beam antennas and onboard packet processing and switching, has helped validate the technical merits of onboard digital processing, which enables efficiencies and new services (such as point-to-point single-hop mesh connectivity).
In order to address the complexities encountered with large, broad-based private networks, what is needed are approaches for a private software defined satellite network (SDSN) that employs a constellation of airborne network nodes, where all main or central Layer 2 (L2) network nodes are controlled via a centralized System Controller (SC).